Got hit with a last minute requirement on my project - How do I minimize the thrashy impact it has?

• Make sure that communication is extremely good - This is absolutely crucial: Tell every relevant stakeholder on the project that there's this new incoming change that could slow down the project through whatever combination of Work Chat + working meeting + Workplace makes the most sense for you. There is no over-communicating here; circulate the "play by play" of this issue as it unfolds.
• Be proactive - I've seen a lot of XFN come in with a request, we handle it, and they come back with another one a few days later. Try to get all the last minute changes out there at once - Push them to think about other potential last minute requests, so you can handle them all at once as a batch.
• Push back (if you can) - Don't just immediately absorb the request. Bring in senior+ engineers, tech leads, and even your manager so the team as a whole can really understand the consequences of this change. What's the impact if we absorb it? What's the impact if we don't absorb it prior to launch and have it as a fast-follow instead? Make sure that both sides of the coin are really understood by everyone and make an informed decision from there. Publish the results of this discussion to further align the team once the final decision is made.
• Retro, retro, retro - After the dust has settled and you've shipped this project, make sure to cover this in the retro. Deviations from the timeline/roadmap are super important to understand, especially in the world of Meta where you need to move fast. Given that this is shaping up to be a couple days lost, you don't need to spend too much time on it, but if it's something like 2 weeks+, you definitely should spend a ton of time on it in retro.

Here's more resources on being an effective tech lead:

• "How to sequence activities to reduce risk?"
• What Makes A Truly Great Tech Lead - A VP of Engineering's Perspective
• How Do Effective Engineering Leaders Help Their Teams Achieve More?